1. Field of the Invention
The present invention relates to a liquid crystal display device which uses a transmissive or transflective liquid crystal layer.
2. Description of the Related Art
JP-A-2005-275142 discloses a display panel which includes a micro lens array composed of a plurality of micro lenses, each having a flat top, disposed on the backlight side of a liquid crystal display panel in order to expand the viewing angle without reducing the front luminance.
Japanese patent No. 3931989 discloses a display device adapted to improve the efficiency of utilization of light from the illumination device to increase the luminance. This display device includes an illumination device, a display panel having a plurality of pixels, and condensing elements disposed between the illumination device and the display panel. The condensing elements are disposed in association with a transmissive region of the pixels and a converging point of the light emitted from the illumination device is adapted to be formed at the side closer to a viewer than at the side of a display medium layer of the display panel.
As described in these conventional techniques, when a micro lens is applied to a display device, it is necessary to take into consideration the viewing angle, the front luminance, and the efficiency of utilization of light.
The liquid crystal display device disclosed in JP-A-2005-275142 was devised to improve the viewing angle and the front luminance. JP-A-2005-275142 describes an output distribution in which, when the angle seen from the front changes, the luminance of the light having penetrated the liquid crystal display panel changes rapidly and then its change moderates. This is because light which penetrated the flat portion is superimposed with light which penetrated a curved surface of the micro lens. As described above, there arises a problem that the luminance largely changes when the viewing angle is changed and also further problem is that it is difficult to form a micro lens having a flat top.